Process for preparing anhydride polymers and resulting product



United States Patent 3,137,660 PROCESS FUR PRERARHNG ANHYDRIDE POLYMERSAND RESULTING PRODUCT John F. .iones, Cuyahoga Falls, fihio, assignor toThe B. F. Goodrich (Iompany, New York, N.Y., a corporation of New YorkNo Drawing. Filed Dec. 27, 1955, Ser. No. 555,308

40 Claims. (Cl. 260-22) This invention relates to substantially linearand to cross-linked polymers having a series of recurring anhydridelinkages attached to the main polymer chain and to methods of preparingthe polymers and more particularly refers to a polymer having aplurality of recurring linkages, which may be referred to asalpha-methylene glutaric anhydride groups, and to a method of preparingthe polymers from alpha-beta-unsaturated monocarboxylic acids or amixture containing such acids and one or more monomers which arecopolymerizable therewith by using a dehydrating agent during thepolymerization step or by treating a linear or cross-linked polymer orcopolymer of an alpha-beta-unsaturated monocarboxylic acid with adehydrating agent to yield the anhydride form of the polymers. In theabove formula R represents hydrogen, a halogen selected from the classconsisting of hydrogen, chlorine, bromine and fluorine, a -CN group, analkyl group having from 1 to carbon atoms, an aryl group, an aralkyl oran alkaryl group and R represents hydrogen and a halogen selected fromthe class consisting of chlorine, bromine and fluorine.

Prior to my invention neither linear nor cross-linked polymers having aplurality of alpha-methylene glutaric anhydride groups attached to orconstituting an integral part of the main polymer chain could beprepared from alpha-beta-monocarboxylic acids or polymers thereof.Maleic anhydride and other alpha-beta-unsaturated polybasic acids do nothomopolymerize to form polymers in which substantially all carboxylgroups are converted to anhydride linkages, but they will copolymerizeto form copolymers having alternating or random succinic anhydridegroups and carboxyl groups along the main polymer chain.

Alpha-beta-unsaturated monocarboxylic acid anhydrides can be reactedunder certain conditions to form non-linear polymers, but copolymers ofalpha-beta-unsaturated monocarboxylic acid anhydrides with otherunsaturated monomers form highly cross-linked hard resins which aresubstantially infusible and difiicultly soluble, as described in US.Patent 2,321,728.

The linear, non-cross-linked polymers of my invention by contrast, arepermanently fusible and readily dissolved in many solvents, and arehydrophilic in that they Will dissolve slowly in water with rupture ofthe anhydride groups. To prepare cross-linked polymers which do notundergo chain scission on opening of the anhydride linkages, it isessential that a polyunsaturated cross-linking agent of the typehereinafter described be employed. The degree of cross-linking can beregulated so as to control to some degree the hydrophilic properties ofthe polymers.

An object of this invention is the provision of substantially linearpolymers having a plurality of recurring 3,137,560 Patented June 16,1964 groups along the main polymer chain. In the formula n represents aninteger greater than 1 and X represents terminal group such as hydrogenand it also represents the remainder of the polymer chain.

Another object is the provision of substantially linear polymers ofalph-abeta-unsaturated monocarboxylic acids and copolymers thereofhaving from about 10% to substantially all of the 'carboxyl groups inthe form of anhydride linkages.

Another object is the provision ofsubstantially linear polymers formedby head to toe polymerization of an alpha-beta-unsaturatedmonocarboxylic acid wherein the carboxyl groups are dehydrated toanhydride groups.

Another object is a method of preparing substantially linear polymershaving recurring groups by polymerizing alpha-beta-unsaturatedmonocarboxylic acids in the presence of a dehydrating agent.

Another object is the provision of polymers having recurringalpha-methylene glutaric anhydride linkages along the main polymer chainwhich chain is cross-linked with a compound having a plurality ofpolymerizable unsaturated linkages other than anhydride groups.

Still another object is the provision of a method of preparing anhydridecontaining polymers, as defined above, by carrying out the reaction inthe presence of an acid anhydride under substantially anhydrousconditions.

Yet another object is the provision of a method for forming a pluralityof glutaric anhydride groups on a polymer of an alpha-beta-unsaturatedmonocarboxylic acid by treating the polymer with a dehydrating agent. I

The above objectsare accomplished by (l) polymerizing a substantiallyanhydrous or glacial alpha-beta-unsaturated monocarboxylic acid andsubstituted derivatives thereof in the presence of a polymerizationcatalyst and in the presence of a dehydrating agent which does notcopolymerize with the alpha-beta-unsaturated monocarboxylic acid andremoving the water of dehydration either by azeotropic distillationand/or by chemically combining it with the dehydrating agent or (2) byfirst polymerizing or copolymerizing the alpha-beta-unsaturatedmonocarboxylic acid and thereafter treating the polymer with adehydrating agent.

The recurring alpha-methylene glutaric anhydride groups of the polymercan have other substituents, depending on the monomer or mixture ofmonomers used in preparing the polymer.

The monocarboxylic, alpha-beta-unsaturated acids that can be used inpreparing the polymer have the general structure in which R and R eachhas the same designation as that given above.

Specific compounds which come under this designation include acrylicacid, methacrylic acid, alpha-ethyl, propyl, butyl, amyl, hexyl, heptyl,octyl, nonyl and decyl acrylic acids, alpha-chloro, bromo and fiuoroacrylic acid, alpha-phenyl acrylic acid, alpha-cyano acrylic acid,alphabenzyl acrylic acid, alpha-tolyl acrylic acid, and otheralpha-substituted acrylic acids with hydrocarbon substituents having upto about 10 carbon atoms. The preferred monomers are acrylic acid,methacrylic acid, alpha-chloro acrylic acid and alpha-cyano acrylicacid. The most pre ferred monomers are acrylic and methacrylic acidsbecause of their ready availability, ease of polymerization, andinertness of the main polymer chain. The monomers can be homopolymerizedin which case each R and R of the generic formula will be alike or theycan be copolymerized in any proportion in which case each R and R of thepolymer may be different.

Substantially linear interpolymers of the describedalpha-beta-unsaturated carboxylic acids and other unsaturated compoundscan also be prepared; In preparing these inter-polymers at least onemolar equivalent or more of an acrylic acid, based on the comonomershould be used. The comonomers that can be employed include maleicanhydride, monochloro maleic anhydride, dichloro maleic anhydride,beta-ethyl, propyl, butyl, amyl, hexyl, octyl, nonyl, and decyl acrylicacids, beta-chloro, bromo and fiuoro acrylic and methacrylic acids,crotonic acid, angelic acid, tiglic acid, beta-cyano acrylic andmethacrylic acids, beta-phenyl acrylic acid (cinnamic acid), betabenzylacrylic acid, beta-tolyl acrylic acid, 2,3-diethyl acrylic acid,2,3-dipropyl acrylic acid and other betaor alpha-beta-substitutedacrylic acids with hydrocarbon substituents having up to about carbonatoms, vinyl alkyl ethers, vinyl esters and other unsaturated monomerswhich will copolymerize with acrylic acid, alpha-substituted derivativesthereof and beta-halo acrylic acids.

In place of the monomers mentioned above, homopolymers andinterpolyrners derived therefrom can be treated with a dehydrating agentto form a plurality of anhydride linkages along the main polymer chain.

The dehydrating acid anhydrides that can be employed include those ofsaturated. and unsaturated monoand polybasic carboxylic acids, if theydo not react with the monomeric polymerizable compounds. These includeanhydrides of saturated, monobasic aliphatic acids such as aceticanhydride, propionic anhydride, butyric anhydride, pentanoic anhydride,hexanoic anhydride and higher monocarboxylic saturated aliphatic acidanhydrides. Anhydrides of chlorinated, brominated and fluorinated acidscan also be used.

Anhydrides of saturated polycarboxylic aliphatic acids that can be usedinclude succinic anhydride, glutaric anhydride, adipic, pimelic,suberic, azelaic, sebacic and anhydrides of higher molecular weightdicarboxylic acids which do not normally form internal anhydrides, butact more nearly like anhydrides of mono-carboxylic acids. Theseanhydrides can also be used as dehydrating agents to produce thepolymers of this invention.

In addition to aliphatic anhydrides, the anhydrides of monoandpolycarboxylic aromatic and cyclo aliphatic acids can be employed in thepreparation of the polymers of this invention. These anhydrides includebenzoic anhydride and anhydrides of homologues and ring substitutedbenzoic anhydride, such as the chloro or bromo benzoic anhydrides, thenitro benzoic anhydrides, the toluic or xylylic anhydrides, or nitro orhalogen derivatives thereof. Anhydrides of polybasic aromatic acidsinclude phathalic anhydride, the anhydride of biphenyl o-o'-dicarboxylicacid, pyromellitic anhydride and others.

therefore must be removed from the reaction mixture if polymerization ofthe monomer is to be effected.

Concentrated sulfuric acid or fuming sulfuric acid can also be used asthe dehydrating agent, but the polymer becomes slightly charred, asevidenced by a brownish discoloration. For this reason neither sulfuricacid nor fuming sulfuric acid is a preferred dehydrating agent.

In this specification the term dehydrating agent is intended to includethe acid anhydrides described and acids having a very strong aflinityfor water, such as sulfuric and fuming sulfuric acids. The term acidanhydride is intended to include anhydrides of carboxylic acids,anhydrides of inorganic acids, mixed anhydrides of organic I andinorganic acids of which acid halides are general Cyclo aliphaticanhydrides, that will cause anhydride groups to form along the polymerchain include tetrahydro and hexahydro phthalic anhydrides andhydrocarbon or halogen substituted derivatives thereof.

Other compounds that will serve as dehydrating media are the acidhalides of the organic acid analogues of the anhydrides mentioned above,and particularly the acid chlorides and acid bromides of the acidscorresponding to the anhydrides.

Inorganic dehydrating agents, such as PCl POCl PCl PBr POBr PBr or P 0which on hydration form compounds which do not react with the monomerscan also be employed to prepare the polymer. All these phosphorouscompounds can be classed as inorganic acid anhydrides, since each willreact with water to form one or more inorganic acids. Thionyl chloridecan also be used but the S0 formed is a polymerization inhibitor andexamples and acetyl chloride a specific example and mixed anhydrides ofinorganic acids such as the phosphorous halides and phosphorousoxyhalides which yield a halogen acid and phosphoric acid on hydrolysisand it also includes such mixed anhydrides as thionyl chloride.

In the reaction /2 molar equivalent of a dehydrating anhydride is neededto convert one mole of acrylic acid or its derivatives to the anhydridelinkages. However, it is possible to convert only a portion of theacrylic acid or derivative to the anhydride form in the polymeric state.As little as M; or A molar equivalent of dehydrating anhydride or asmany as two or three molar equivalents for each mole of acrylic acid orderivative can be used. I prefer to use about one to two molarequivalents of dehydrating anhydride for each mole of acrylic acidderivative thereof in preparing the anhydride form polymer. Thedehydrating agent can be added in one lot or it can be proportioned asneeded.

A cross-linked polymer containing linear recurring betamethyleneglutaric anhydride and substituted beta-methyh 'ene glutaric anhydridegroups can be prepared by copolymerizing the alpha-beta-unsaturatedmonocarboxylic acid monomers as defined above with from about 0.01% toabout 30% by weight of a cross-linking agent, based on the weight of thealpha-beta-unsaturated monocarboxylic acid monomers. The cross-linkedpolymers can be employed to make stable viscous mucilages in alkalineaqueous media.

The cross-linking agents may be defined as compounds having a pluralityof terminal CH =C groups. They include polyunsaturated hydrocarbons suchas divinyl cyclohexane; low molecular weight conjugated dienes, such aspolybutadiene and other conjugated diene polymers having substantialunsaturation in the polymer molecule, sulfones, such as the polyallyltrimethyl trisulfones, particularly hexaallyl trimethylene trisulfone;unsaturated amides such as trimethacrylyl triazine andmethylene-bisacrylamide; diand polyunsaturated esters, such asethylpartial others of polyhydric alcohols, such as diallyl glyc- Verol, polyallyl sucrose having 3 to 6 allyl groups per sucrose molecule,triand tetraallyl erythritol, triand tetraallyl pentaerythritol, tri-,tetra-, penta and hexaallyl sorbitol or mannitol, polyallyl glucose,polyallyl levulose, polyallyl mannose, polyallyl gulose, polyallylthreose, polyallyl erythrose, polyallyl arabinose, polyallyl ribose,polyallyl xylose, polyallyl galactose, polyallyl lactose and otherpolyethers of mono-, diand triand higher saccharides or oligosaccharidesall of which contain at least three allyl groups per sugar molecule.

The method of preparing both the linear and cross linked anhydridepolymers from the monomers comprises polymerizing analpha-beta-unsaturated monocarboxylic acid, and a comonomer if one isused, preferably in an inert solvent such as benzene, hexane, acetone,carbon tetrachloride, ethylene chloride or other known inert nonaqueoussolvent in the presence of a free radical catalyst, such as benzoylperoxide, caprylyl peroxide and azo-bisisobutyronitrile, and also in thepresence of a dehydrating agent, such as a carboxylic anhydride, an acidhalide, such as an acid chloride or P Thetemperature of the reaction canbe held at about 50 C. or below or it can be elevated to 70-100" C.However, I prefer to initiate the reaction at a temperature of 50 55 C.The reaction is fairly rapid and is complete within a few hours. Themechanism by which anhydride groups are formed on a linear polymer isnot understood, since anhydride formation appears to proceedsubstantially simultaneously with polymer formation. When thepolymerization reaction is carried out in a solvent for the monomers anda non-solvent for the polymers, the anhydride linkages are present onthe polymer as it precipitates from the reaction mixture.

Anhydride groups can be formed'on a carboxylic polymer in which adjacentcarboxyl groups are separated by a maximum of three carbon atoms in thepolymer chain by treating the polymer with any of the dehydrat,

ing agents mentioned above.

The anhydride polymers are substantially insoluble in hydrocarbon andhalogenated hydrocarbon solvents.

The polymers of this invention can be extruded to form hydrocarbonresistant tubing. The anhydride polymers adhere strongly to aluminum,iron and brass. The anhydride films of the linear polymers can be fusedonto the metals to provide solvent resistant coatings for benzene orhexane tanks. The cross-linked polymers do not dissolve in any knownsolvent, but the partial alkali metal salts form very viscous mucilagesin aqueous media. The rnucilages at concentrations of from 0.5 to 1% areex cellent thickening agents for water systems and suspending agents forwaterinsoluble materials.

The following examples are intended to illustrate more fully thepreparation of the linear anhydride according to the method of thisinvention but are not to be construed as a limitation on the scopethereof, for there are, of course, numerous possible variations andmodifications of proportions and reaction conditions which will giveoperable results.

In the examples the parts are by weight unless otherwise specified.

EXAMPLE I A mixture of about 90% of acetic anhydride and about glacialacrylic acid, containing from about 1 to about 2% by weight of water and98-99% acrylic acid, was prepared. To this mixture about 2% benzoylperoxide based on the acrylic acid was added. The acrylic acid was thenpolymerized in a nitrogen atmosphere at a temperature of about 50 C. for16 hours.

A white flufiy polymer precipitated and was separated from the liquid byfiltration and dried in an oven at 50-60 C.

The polymer was readily soluble in dirnethyl formamide,gamma-butyrolactone, nitromethane and N-methyl pyrrolidone. It also wentinto solution slowly in water and dilute aqueous NaOI-I. It is believedthat the anhydride linkage of the polymer is slowly ruptured by waterand aqueous alkali to form, respectively, partial acids and partialsalts.

These solubility characteristics clearly indicate that the polymerformed was substantially linear.

The cation capacity of the polymer was 15.82 milliequivalents per gram,as compared to a theoretical value of 15.87 for polyacrylic anhydrideand 13.8 for polyacrylic acid.

.6 This polymer therefore consisted of a plurality of recurringoH,-ooHio- O=C0 0=o groups, with practically no free carboxyl groups.

EXAMPLE II A mixture of 10% glacial acrylic acid, benzene and 1 mole ofacetic anhydride for each mole of acrylic acid was polymerized in aninert atmosphere in the presence of 2% benzoyl peroxide, based onacrylic acid.

The polymerization temperature was 5 0 C. The polymer Wl'llCh wasinsoluble in the liquid reaction medium had the same solubilitycharacteristics as those described under Example I.

EXAMPLE III The proportions and conditions of Example II were used withthe exception of the catalyst, which consisted of 2% of caprylylperoxide.

The solubility characteristics of the polymer were extremely similar tothose described for Example I, and the cation capacity was 15.45 meq./g.

EXAMPLE IV Hexane was used as the reaction medium in place of benzene.The remaining ingredients, proportions and conditions were the same asthose described for Example III. The polymer which resulted Was solublein the solvents listed under Example I and the cation capacity was 15.81meq./g.

EXAMPLE V Acetone was employed as the reaction medium diluent in placeof hexane, but otherwise the ingredients, proportrons and reactionconditions were similar to those of Example IV. The polymer which wasformed had solubility characteristics of the polymer of Example I. Thecation capacity was 15 .07 meq./ g.

EXAMPLES VI-X In the following series of examples, polymerization of a10% by weight solution of glacial acrylic acid in 90% by weight benzeneWas carried out in the presence of 2% azo-bis-isobutyronitrile catalyst(Porofor N). One mole of dehydrating agent was employed for each mole ofacrylic acid.

Each polymer was extracted with benzene to remove all the dehydratingagent and the acid that resulted from hydrolysis of the dehydratingagent. It is apparent from these data that the polymer in all instancesis linear. The cation capacity of each polymer was well over 15.10meq./g. showing that a very high proportion of the carboxyl groups wereconverted to anhydride linkages.

EXAMPLES XIXIV Polymethacrylic anhydride can be made by polymerizingglacial methacrylic acid in the presence of a dehydrating agent, in amanner very similar to that described for acrylic acid.

The proportions of methacrylic acid and diluent were 1 to 9. The molarratio of dehydrating agent to glacial methacrylic acid was about 1 to 1.

The results of a series of tests using acetic anhydride as thedehydrating agent are listed in the following table.

Table II Ex. Reaction Catalyst Tcrnp., Solubility of Diluent; O. PolymerXI Benzene-.- 2% benzoyl 50 Solubleinaqueous peroxide alkali H O,dimethyl tormamide and gamma bu tyrolactone XII do 2% Porofor N... 50Do.

XIII..- HQX3I19 o 50 D0.

XIV.-. Acetone..- do 50 Do.

Each of these polymethacrylic anhydrides was slightly soluble inN-methyl pyrrolidone, but the solubility was lower than that ofpolyacrylic anhydride. At high concentrations the polymethacrylicanhydride was not truly soluble in N-methyl pyrrolidone, as evidenced byswelling and greatly increased viscosity.

The cation capacity of the polymers was at least 12.5 meq./ g. orhigher. The calculated valuefor polymethacrylic anhydride is 12.82 meq./g. and that of polymethacrylic acid is 11.6 meq./g.

The methacrylic acid used in the preparation of the polymer containedbetween 1 and 2% Water.

EXAMPLES XV-XXII A group of copolymers containing acrylic andsubstituted acrylic anhydride linkages were prepared in benzene with 1mole of acetic anhydride per mole of monomer as the dehydrating medium.The glacial monomerdiluent mixture ratio was 1 to 9. In each instancethe catalyst was azo-bis-isobutyronitrile at a concentration of 2% basedon the monomers. The temperature of polymerization was 50 C. None of themonomers contained more than 5% water.

Ex. Monomers Solubility XV 75% acrylic acid, 25% methacrylic Soluble inWater and aci aqueous alkali.

XVI 5U%%cry1ic acid, 50% methacrylic Do.

aci

XVII. 25% a1crylic acid, 75% methacrylic Do.

aci

XVIII- 7 5% acyrlic acid, 25 acrylic anhy- Slight gel in gamma ridebutyrolactoue.

XIX 50% acrylic acid, 25% mcthacrylic D0.

acid, 25% acrylic anhydride.

XX 75% acrylic acid, 25% alpha-bromo Soluble in gamma acrylic acid.butyrolactonc.

XXI 75% methacrylic acid, 25% alpha- Do.

bromo acrylic acid.

XXII. 25%aicrylic acid, 75% methacrylic Do.

aci

The solubility characteristics indicate that the copolymers in whichacrylic anhydride was employed as a monomer, cross-linking has occurred.The amount of cross-linking, however, is insuiiicient to preventsolubility of the polymers in aqueous alkaline media but is sufficientto produce a slight gel in gamma butyrolactone. Usually the masscopolymerization of such a high proportion of acrylic anhydride, witheither acrylic acid or methacrylic acid in the absence of a dehydratingagent results in a hard, highly cross-linked infusible and completelyinsoluble polymer.

The cation capacities of all these polymers were very near thetheoretical value. For example, that of EX- ample XVI was 14.29 meq./ g.and that of Example XV H was 13.59 meq./g. 7

EXAMPLE XXIII Linear anhydride copolymers with other monounsatu ratedacids or anhydrides can also be prepared. A monomeric mixture of 75parts glacial acrylic acid and 25 parts maleic anhydride was polymerizedin an inert atmosphere in benzene at a temperature of 50 C. in thepresence of one mole of acetic anhydride for each mole of acrylic acidand 2% azo-bis-isobutyronitrile. The resulting polymer was linear asindicated by its solubility in gamma butyrolactone, aqueous alkali,dimethyl formamide and N-methyl pyrrolidone. The cation capacity agreedvery closely with the calculated values for a copolymer having the sameratio of anhydride groups in the polymer chain as that which shouldbepresent from the proportions of maleic anhydride and convertedcarboxyl groups of the monomeric mixture prior to polymerization.

EXAMPLE XXIV Monomeric glacial acrylic acid and crotonic acid, which isa beta-methyl acrylic acid, were reacted to yield a linear, anhydridecopolymer. The monomeric mixture contained 75% acrylic acid and 25%crotonic acid. The polymerization was effected in an inert atmosphere inbenzene at a temperature of 50 C. in the presence of 2%azo-bis-isobutyronitrile. One mole of acetic anhydride was used as adehydrating agent for each mole of acrylic acid.

The copolymer was soluble in water, aqueous alkali, dimethyl formamideand N-methyl pyrrolidone. The cation capacity of the copolymer was ingood agreement with the calculated value, based on the monomericmixture.

EXAMPLE XXV A linear anhydride copolymer was prepared in an inertatmosphere from a monomeric mixture of 75% glacial acrylic acid and 25%sorbic acid. The reaction diluent, by volume was benzene, the catalyst,azo-bis-isobutyronitrile, was employed in a 2% concentration, and thereaction temperature was about 50 C. The copolymer was soluble in thesolvents mentioned in Example XXIV and its cation capacity showed thatthe carboxyl groups of both acidic monomers were converted substantiallycompletely to anhydride linkages.

EXAMPLES XXVI-XXXVI Anhydride polymers with controlled amounts ofcrosslinking to make the resulting copolymers either watersensitive,i.e., swellable in water without true solution, or substantiallywater-insensitive and insoluble in ordinary solvents, can be made bycopolymerizing acrylic acid, methacrylic acid or the other substitutedmonomeric derivatives of acrylic acid mentioned above, with a crosslinkagent in the presence of a polymerization catalyst and an acidanhydride, which will not react with the polymerizable monomers, as adehydrating agent.

A series of cross-linked polyacrylic anhydrides were made with varyingamounts of cross-linking agents to yield polymers whose partial salts(75%) had properties varying from water-insensitivity to those whichformed highly viscous mucilages at low concentrations in water.

Tabulated below are the characteristics of copolymers prepared byreacting acrylic acid and allyl sucrose containing an average of about5.8 allyl groups per sucrose molecule. The polymerization was eiiectedin benzene in the presence of 2% peroxide and one mole of aceticanhydride for each mole of acrylic acid.

The polymers which are cross-linked with 10% or more of allyl sucrosecontaining a plurality of allyl groups are not swellable in water, areinsoluble in ordinary solvents, and are infusible. The can serve as ionexchange resins. The polymers containing or less of the allyl sucrosecross-linking agent swell in water to form viscous mucilages which actas suspending and emulsion stabilizing agents.

EXAMPLE XXXVII Another cross-linked, anhydride polymer was made bycopolymerizing acrylic acid with 2% methylene-bis-acrylamide in benzenein the presence of a mole of acetic anhydride for each mole of acrylicacid. The reaction temperature was 50 C., and the catalyst was benzoylperoxide in a concentration of 2% The 75% neutralized polymer (usingaqueous NaOH as the neutralizing medium) had a viscosity of 43, and 2 in1.5, 1.0 and 0.5% concentrations, respectively, in water.

EXAMPLES XXXVIlI-XLIV Other cross-linking agent can be used in preparingwater sensitive polymers from acrylic acid. Tabulated below are theresults obtained in preparing polymers with various cross-linkingagents. The amount of cross-linking agent in each case was 2% by weightof the polymerizable comonomer or mixture of comonomers. The reactionwas run at 50 C. in benzene as a diluent. Acetic anhydride in equimolarratios with the acrylic acid was the dehydrating agent. Mucilages inwater of the 75 sodium salt were prepared.

It is apparent from these data that cross-linking agents withhydrophilic properties are more desirable for preparing copolymers wherewater-sensitive or water-swellable characteristics are desired. Divinylbenzene will react with acrylic or methacrylic acid, but the swellingcharacteristics of the resulting polymer in water are not great. Ingeneral also, cross-linked methacrylic acid and methacrylic anhydridepolymers have lower swelling power in aqueous media than the acrylicacid polymers made by this method. It is to be understood that othermonomers which will copolymerize with arcrylic acids as describedheretofore can be used for preparing the crosslinked anhydride polymers.

EXAMPLE PGJV mer had a cation capacity of 14.08 meq./ g. The polymer wassoluble in gamma-butyrolactone.

l 10 EXAMPLES XLVI-XLVIII Glacial acrylic acid (1 part) was polymerizedin benzene (9 parts in the presence of an equivalent proportion based onacrylic acid, of PCl PCI;; and POCl respectively, using 2% caprylylperoxide as a polymerization catalyst. The eractions were run at 50 C.Each polymer settled to the bottom of the reaction flask as a very finepowder.

The anhydride polymer made with PCl as the dehydrating agent containedabout 4.9% acid chloride linkages, based on the chlorine analysis, andthe cation capacity of the polymer Was 16.31 meq./ g. The polymer madewith POCl as the dehydrating agent had a cation capacity of 14.99meq./g. and only very slight traces of chlorine could be detected in thepolymer. All three anhydride containing polymers were soluble ingammabutyrolactone.

EXAMPLE XLIX a cation absorption capacity of 15.83 meq./g. showing thatthe polymer contained only a very small proportion of free carboxylgroups and well over anhydride linkages. The polymer was soluble ingamma-butyrolactone and dimethyl formamide showing that it was linear.

EXAMPLE L The procedure of Example XLIX was followed with glacialmethacrylic acid in place of acrylic acid. The polymer contained tracesof chlorine and had a cation absorption capacity of 13.1 meq./ g.

These examples clearly indicate that the polymer which forms under thereaction conditions of this invention contain a plurality of methyleneglutaric anhydride linkage along the main polymer chain.

Carboxyl groups of alpha-beta-unsaturated monocarboxylic acid. polymerscan be converted to anhydride groups by use of the same dehydratingagents as those employed in preparing polymeric anhydrides frommonomeric alpha-beta-unsaturated monocarboxylic acids. In generalthe'treatment of polymers of alpha-beta-unsatw rated monocarboxylicacids requires a fairly long period of treatment with a dehydratingagent to get substantial conversion of the free carboxyl groups toanhydride linkages and attainment of conversion to anhydride is possibleonly after protracted treatment with an acid anhydride.

EXAMPLE LI Polyacrylic acid was prepared by polymerizing glacial acrylicacid in benzene as a diluent in the presence of 2% benzoyl peroxide at50 C. A 10% slurry of the polymer in benzene was treated with oneequivalent of thionyl chloride under reflux for 4 hours. The so treatedpolymer had a cation capacity of 14.71 meq./ g. The chlorine content was0.l6%. These data show that the polymer contained 58% anhydride groups,a trace of (about 0.4%) acid chloride groups and 41.6% free carboxylgroups. The reacted polymer was soluble in gamma-butyrolactone andN-methyl pyrrolidone.

EXAMPLE LII A 10% slurry of polyacrylic acid in benzene was reacted withtwo equivalents of acetic anhydride at 50 C. for 16 hours. The reactedpolymer had a cation capacity of 14.28 meq./ g. and was soluble ingamma-butyrolactone and N-methyl pyrrolidone.

1 1 EXAMPLE L111 Polyrnethacrylic acid was prepared by the proceduredescribed in Example LII. A slurry in benzene was treated for 24 hoursat 50 C. with two equivalents of acetic anhydride. The thus treatedpolymer had a cation capacity of 12.39 meq./ g. indicating that 35% ofthe carboxyl groups were converted toanhydride linkages.

Polymers of other substituted acrylic acids as defined heretofore can besubstituted for polymethacrylic acid to produce corresponding anhydridecontaining polymers. These include polyalpha-chloro-acrylic anhydride,polyalpha-bromo-acrylic anhydride, polyalpha-fluoro-acrylic anhydride,polyalpha-cyano-acrylic anhydride, polyethacrylic anhydride,polyalpha-phenyl-acrylic anhydride. Copolymers of acrylic or substitutedacrylic acids with other alpha-beta-unsaturated monomers described abovecan also be given treatments such as those above to yield polymershaving a plurality of alpha-methylene glutaric anhydride linkages alongthe main polymer chain.

In both the linear and cross-linked polymers and interpolymers thealpha-methylene glutaric anhydride linkages are spaced along the mainpolymer chain and are not part of the cross-linking structure,Cross-linking when desired can be very effectively controlled by the useof a poly-' unsaturated monomer of the type described above andcopolymerizing it with the alpha-beta-unsaturated monocarboxylic monomertherewith under dehydrating conditions. The cross-linked structure whichresults has linear stability in that opening of the anhydride groupsdoes not result in a decrease in molecular Weight of the originalcross-linked polymer.

The proportion of carboxyl groups converted to anhydride linkages on themain polymer chain can vary from about 10% to about 100% by controllingthe conditions under which the anhydride groups are formed. Thus, if itis desired to make a polymer with from 10 to about of the carboxylgroups converted to anhydride this can be efiected quite readily bytreating the polymer with an acid anhydride. To get substantially all ofthe carboxyl groups in anhydride form it is most simple to start withthe monomers and carry out the polymerization in the presence of excessdehydrating agent. Use of less than the theoretical amount ofdehydrating agent will usually result in a polymer having less than allof its carboxyl groups converted to anhydride linkages. By controllingthe amount of dehydrating agent the proportion of carboxyl groupsconverted to anhydride can also be controlled with a fair degree ofaccuracy.

I claim:

1. A method for preparing polymers having a plurality of recurringalpha-methylene glutaric anhydride groups as part of the main chainthereof, comprising treating under substantially anhydrous conditions amember selected from the class consisting of (A) (1) at least onesubstantially anhydrous monomeric monocarboxylic acid having from 3 to13 carbon atoms and a terminal CH group in a position beta to thecarboxyl group as the sole aliphatic carbon-to-carbon unsaturation andcontaining only the elements carbon, hydrogen, oxygen and not more than1 halogen in the alpha position, (2) mixtures of a major proportion of(1) with at least one other monoolefinic monomer which iscopolymerizable with (l), (3) mixtures of (l) and .01 to by weight basedon said (1) of a polyunsaturated monomer which is copolymerizable withsaid (1), and (4) mixtures of (2) with .01 to 30% by weight based onsaid (2) of a polyunsaturated monomer which is copolymerizable with said(2), in the presence of a free radical catalyst and at a polymerizingtemperature, and (B) polymers of said (A) at an elevated temperature,with (C) at least one mole of a dehydrating agent per molar equivalentof carboxyl in said (A) and (B), said dehydrating agent being selectedfrom the class consisting of non-polymerizable carboxylic anhydrides ofacids having at least 2 carbon atoms and up to about 18 carbon atoms,acid halides of said non-polymerizable l 2 acids, phosphorus halides,phosphorous oxyhalides, sulfur oxyhalides, wherein the halogen of saiddehydrating agent has an atomic weight of from about 35.5 to about and P0 said (B) being treated for a time sufiicient to convert at least about35% of the carboxyl groups to anhydride groups on the main polymerchain.

2. A method of preparing polymers having a plurality of recurringalpha-methylene glutaric anhydride groups as part of the main chainthereof comprising polymerizing under substantially anhydrous conditionsin the presence of a free radical polymerization catalyst at atemperature between 0 to C. at least one substantially anhydrousmonomeric monocarboxylic acid having from 3 to 13 carbon atoms and aterminal CH group in a position alphabeta to the carboxyl group as thesole aliphatic carbonto-carbon unsaturatio-n, with at least one mole foreach mole of said monocarboxylic acid of a dehydrating agent selectedfrom the class consisting of non-polymerizable :omprising polymerizing asubstantially anhydrous monomer comprising acrylic acid in the presenceof from about 1 to about 3 moles based on the acrylic acid of aceticanhydride.

4. The method steps of claim 3 in which the monomer comprisesmethacrylic acid.

5. The method steps of claim 3 in which the monomers comprise a mixtureof acrylic and methacrylic acids.

6. The method steps of claim 3 in which the monomers comprise a mixtureof acrylic acid and alpha-bromo acrylic acid.

7. The method steps of claim 3 in which the monomers comprise a mixtureof methacrylic acid and alphabromo acrylic acid.

8. The method steps of claim 3 in which the monomers comprise a mixtureof acrylic acid and maleic anhydride.

9. A method of preparing a polymer having a plurality of carboxylicanhydride linkages on the main polymer chain comprising treatingpolyacrylic acid with. acetic anhydride for a time and at a temperaturesuflicient to' convert at least 10% of the carboxyl groups of thepolymer to anhydride groups.

10. The method steps of claim 9 in which the polymer is polymethacrylicacid.

11. The method steps of claim 9 in which the polymer is a copolymer ofacrylic and methacrylic acids.

12. The method of claim 9 in which the dehydrating agent is phthalicanhydride.

13. The method of claim 11 in which the dehydrating agent is phthalicanhydride.

14. The method of claim 10 in which the dehydrating agent is P 0 15. Themethod of claim 11 in which the dehydrating agent is P205.

16. A method of preparing a cross-linked polymer containing a pluralityof recurring alpha-methylene anhydride groups comprising polymerizing asubstantially anhydrous monomeric mixture containing (l) a majorproportion of at least one monocarboxylic acid having from 3 to 13carbon atoms and a terminal CH group in a position alpha-beta to thecarboxyl group as the sole aliphatic unsaturation and (2) from about 0.1to about 30% by weight based on (1) of a polyunsaturated compoundselected from the class consisting of polyallyl ethers ofoligosaccharides, polyallyl trimethylene trisulfone, triacrylyltriazine, methylene bis-acrylamide, betastyryl acrylic acid, divinylether, l,4,5,8-naphthalene tetravinyl ether, divinyl ketone, diallylketone, and low molecular weight polymersof conjugated dienehydrocarbons having substantial unsaturation in the polymer molecule,said polymerization being effected in the presence of a free radicalpolymerization catalyst, and in the presence of at least one mole permolar equivalent of carboxyl in said monomeric mixture of a memberselected from the class consisting of non-polymerizable carboxylicanhydrides of acids having at least 2 carbon atoms and up to 18 -carbonatoms, acid halides of said non-polymerizable acids, P phosphoroushalides, phosphorous oxyhalides, and sulfur oxyhalides wherein thehalogen has an atomic weight of from about 35.5 to about 80.

17. The method of claim 16 in which the polymerizable acid is acrylicacid.

18. The method of claim 16 in which the polymerizable acid ismethacrylic acid.

19. The method of claim 16 in which the dehydrating agent is aceticanhydride.

20. The method of claim 17 in which the dehydrating agent is aceticanhydride.

21. The method of claim 18 in which the dehydrating agent is aceticanhydride.

22. The method of claim 19 in which the cross-linking ingredient ispolyallyl pentaerythritol.

23. The method of claim 20 in which the cross-linking ingredient ispolyallyl sucrose having at least three allyl groups per sucrosemolecule.

24. The method of claim 21 in which the cross-linking ingredient ispolyallyl pentaerythritol.

25. The method of claim 21 in which the cross-linking ingredient ispolyallyl sucrose having at least three allyl groups per sucrosemolecule.

26. The method of claim 16 in which the cross-linking ingredient ismethylene-bis-acrylamide and the dehydrating agent is acetic anhydride.

27. The method of claim 26 in which the polymerizable acid is acrylicacid.

28. The method of claim 26 in which the polymerizable acid ismethacrylic acid.

29. A composition having a plurality of alpha-methylene glutaricanhydride groups selected from the class consisting of (1) linearhomopolymers of a monocarboxylic acid having from 3 to 13 carbon atomsand a CH group in the position beta to the carboxyl group as the solealiphatic unsaturation and having from about 35 to 100% of the carboXylgroups converted to said alphamethylene glutaric anhydride groups, (2)linear interpolymers of a major proportion of the monocarboxylic acidsdefined in (l) and another monomer copolymerizable with the unsaturatedacids in said (1) and having from about 35 to 100% of the carboxylgroups of said interpolymers converted to alpha-methylene glutaricanhydride groups, (3) cross-linked interpolymers of the acids in said(1) and from about .1 to about 30% by weight based on the unsaturatedacids defined in said (1) of a polyunsaturated cross-linking agent otherthan a polyunsaturated anhydride of a carboxylic acid, said crosslinkedinterpolymer defined in (3) having from about 35 to about 100% of itscarboxyl groups converted to alphamethylene glutaric anhydride groups,and (4) crosslinked interpolymers of a major proportion of themonocarboxylic acids defined in 1) another monomer copolymerizable withthe unsaturated acids in said (1) and from about 0.1 to about 30% byweight based on the weight of the combined weight of the copolymerizableacids and other monomer defined in (4) of a polyunsaturatedcross-linking agent other than a polyunsaturated anhydride of acarboxylic acid, the said cross-linked interpolymer refined in (4)having from about 35 to about of its carboxyl groups converted toalphamethylene glutaric anhydride groups.

30. A linear anhydride of polyacrylic acid having from 35% to 100% ofthe carboxyl groups on the polymer converted to anhydride groups.

31. A linear anhydride of polymethacrylic acid having from 35 to 100% ofthe carboxyl groups on the polymer converted to anhydride groups.

32. A. linear copolymer of acrylic and methacrylic acids having from 35to 100% of the carboxyl groups converted to anhydride groups.

33. A linear copolymer of acrylic acid and an alphachloro acrylic acidhaving from 35% to 100% of the carboxyl groups converted to anhydridelinkages.

34. A linear copolymer of acrylic acid and maleic anhydride having from35 to 100% of the carboxyl groups of the acrylic acid moiety convertedto anhydride groups.

35. A cross-linked interpolymer of acrylic acid and 0.1

to 30% by Weight of polyallyl pentaerythritol in which from 35 to 100%of the carboxyl groups are converted to anhydride groups.

36. A cross-linked interpolymer of acrylic acid and 0.1 to 30% by weightof polyallyl sucrose having at least three allyl groups per sucrosemolecule said polymer having from 35 to 100% of the carboxyl groupsconverted to anhydride groups.

37. A cross-linked interpolymer of acrylic acid and from 0.1 to 30% byweight of polyallyl phloroglucinol in which 35% to 100% of the carboxylgroups are converted to anhydride groups.

38. A cross-linked interpolymer of methacrylic acid and from 0.1 to 30%by weight of polyallyl pentaerythritol having from 35% to 100% of thecarboXyl groups converted to anhydride groups.

39. A cross-linked interpolymer of methacrylic acid and from 0.1 to 30%by weight of polyallyl sucrose having at least 3 allyl groups persucrose molecule, said interpolymer having from 35 to 100% of thecarboxyl groups converted to anhydride groups.

40. A cross-linked interpolymer of methacrylic acid and from 0.1 to 30%by weight of polyallyl phloroglucinol, said interpolymer having from 35to 100% of the carboxyl groups converted to anhydride linkages.

References Cited in the file of this patent UNITED STATES PATENTS2,259,512 Barnes Oct. 21, 1941 2,308,581 Barnes Ian. 19, 1943 2,312,565McDowell et al. Mar. 9, 1943 2,336,985 Freund Dec. 14, 1943 2,402,604Coifman June 25, 1946 2,798,053 Brown July 2, 1957 FOREIGN PATENTS450,455 Great Britain July 15, 1936 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,137,660 June 16, 1964 John F.Jones It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

Column 2, lines 16 to 21, the formula should appear as shown belowinstead of as in the patent:

column 4, line 64, for "monallyl" read monoallyl column 9, line 19, for'"agent" read agents column 14, line 7, for "refined" read defined samecolumn 14, line 55, for

"2,312,565" read 2,313,565

Signed and sealed this 3rd day of November 1964,

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. A METHOD FOR PREPARING POLYMERS HAVING A PLURALITY OF RECURRINGALPHA-METHYLENE GLUTARIC ANHYDRIDE GROUPS AS PART OF THE MAIN CHAINTHEREOF, COMPRISING TREATING UNDER SUBSTANTIALLY ANHYDROUS CONDITIONS AMEMBER SELECTED FROM THE CLASS CONSISTING OF (A) (1) AT LEAST ONESUBSTANTIALLY ANHYDROUS MONOMERIC MONOCARBOXYLIC ACID HAVING FROM 3 TO13 CARBON ATOMS AND A TERMINAL CH2= GROUP IN A POSITION BETA TO THECARBOXYL GROUP AS THE SOLE ALIPHATIC CARBON-TO-CARBON UNSATURATION ANDCONTAINING ONLY THE ELEMENTS CARBON, HYDROGEN, OXYGEN AND NOT MORE THAN1 HALOGEN IN THE ALPHA POSITION, (2) MIXTURES OF A MAJOR PROPORTION OF(1) WITH AT LEAST ONE OTHER MONOOLEFINIC MONOMER WHICH ISCOPOLYMERIZABLE WITH (U), (3) MIXTURES OF (1) AND 901 TO 30% BY WEIGHTBASED ON SAID (1) OF A POLYUNSATURATED MONOMER WHICH IS COPOLYMERIZABLEWITH SAID (1), AND (4) MIXTURES OF (2) WITH .01 TO 30% BY WEIGHT BASEDON SAID (2) OF A POLYUNSATURATED MONOMER WHICH IS COPOLYMERIZABLE WITHSAID (2), IN THE PRESENCE OF A FREE RADICAL CATALYST AND A POLYMERIZINGTEMPERATURE, AND (B) POLYMERS OF SAID (A) AT AN ELEVATED TEMPERATURE,WITH (C) AT LEAST ONE MOLE OF A DEHYDRATING AGENT PER MOLAR EQUIVALENTOF CARBOXYL IN SAID (A) AND (B), SAID DEHYDRATING AGENT BEING SELECTEDFROM THE CLASS CONSISTING OF NON-POLYMERIZABLE CARBOXYLIC ANHYDRIDES OFACIDS HAVING AT LEAST 2 CARBON ATOMS AND UP TO ABOUT 18 CARBON ATOMS,ACID HALIDES OF SAID NON-POLYMERIZABLE ACIDS, PHOSPHORUS HALIDES,PHOSPHOROUR OXYHALIDES, SULFUR OXYHALIDES, WHEREIN THE HALOGEN OF SAIDDEHYDRATING AGENT HAS AN ATOMIC WEIGHT OF FROM ABOUT 35.5 TO ABOUT 80AND P2O5 SAID (B) BEING TREATED FOR A TIME SUFFICIENT TO CONVERT ATLEAST ABOUT 35% OF THE CARBOXYL GROUPS TO ANHYDRIDE GROUPS ON THE MAINPOLYMER CHAIN.